The invention concerns a method and device for heat treatment of bodily tissue.
Heat treatment yields good treatment results with certain types of disease conditions involving unnatural growth of tissue. The tissue is heated to the extent that it dies. Examples of such disease conditions are certain types of cancer and benign prostate hyperplasy, BPH. During treatment certain portions of the tissue are heated so that tissue death ensues, while other portions of tissue must or should be protected. The temperature in the area of treatment should amount to at least 50xc2x0 C. The duration of treatment is typically 1 hour but could be shorter. The disease conditions which are primarily indicated are those which occur in tissue surrounding cavities in the body, such as the prostate gland.
Different devices can be used in order to induce heating. Devices for heating by means of laser as well as with microwaves and radio frequencies are common.
Heat treatment with a treatment catheter that is equipped with a microwave antenna is also known with the mentioned course of disease. Characteristic for previously known microwave treatment is that the prostate tissue is heated with microwaves. The intention is to heat parts of the prostate gland so that the tissue coagulates, i.e. dies. Examples of such microwave treatment are known previously through U.S. Pat. No. 5,480,417 and U.S. Pat. No. 5,234,004. The element that emits the microwave radiation consists of a coaxial cable that is included in a catheter for treatment. Cooling fluid circulates through the catheter. The intention with the cooling is to protect the prostatic urethra, that is to say the part of the urethra that runs through the prostate gland, from being affected and damaged by the heat that is generated by the microwaves. Another reason for cooling the catheter is to transport away waste heat in the coaxial cable. Also, cooling of the catheter has been suggested to yield pain relief, the effect being uncertain.
It has long been viewed as important to protect the prostatic urethra during microwave treatment of benign prostate enlargement. This protection of the prostatic urethra hinders the treatment from being really effective, however, since parts of the obstructing tissue closest to the urethra are not heated sufficiently but remain unaffected because of the cooling. The clinical result of heat treatment of the kind envisioned here is dependent on the amount of tissue that coagulates. The degree of coagulation depends in turn on temperature in combination with the length of treatment. The temperature in turn depends on the input of energy and the heat dissipation by the blood flow. If the purpose of cooling the prostatic urethra is to protect the urethra from destruction, the transport of heat energy away from the area of treatment is increased, which is counterproductive and in the end diminishes the efficiency of the treatment.
A medical device is known from U.S. Pat. No. 5,366,490. The device comprises a catheter that can be inserted through urethra to the prostate. A control channel for an extendible needle runs through the catheter. The needle may be equipped in its tip portion with, or designed as, a needle antenna for microwaves. The tip portion can extend into the prostate tissue. According to an alternate embodiment the needle may instead be hollow and used for the supply of treatment fluid to destroy cells in the prostate tissue. Pain relief is achieved in accordance with U.S. Pat. No. 5,366,490 by supplying a gel or similar into the urethra and, in the case of severe pain, by administering an anesthetic to the patient.
Problems may arise with different forms of heat treatment of BPH due to a large blood flow in the prostate tissue. A large blood flow results namely in heat from the treatment catheter being directed away from the tissue that was meant to be heated. This may lead to a problem with increased time for treatment or that the efficiency of the treatment deteriorates. Another aggravating circumstance is the fact that blood flow varies greatly from one individual to the other.
By measuring the temperature in the prostate tissue during treatment and by using a stronger or more directed supply of heat in those cases when the temperature does not increase in a desirable way, it is possible to maintain an acceptable result of treatment. Stronger supply of heat raises the temperature in certain portions of the prostate tissue. Treatment given in particular in the case of such further increased temperature may lead to severe pain in patients. In order to lessen such pain to some extent, a pain-relieving agent is generally administered in various ways preoperatively. It is for instance common to insert a gel containing an analgesic substance into and through the penis and urethra to an area around the prostate. Thus, a good analgesic effect can be obtained in the urethra. During the subsequent treatment the prostate tissue will, however, also be heated, which can result in the patient experiencing pain despite the preventive pain relief procedure.
Prior to this type of treatment of the prostate it is preferable to drain the urinary bladder. This is usually implemented by inserting a urinary catheter of conventional type through the urethra, so that one end thereof reaches into the urinary bladder. Upon emptying of the urinary bladder the catheter is removed and a treatment catheter is instead inserted into urethra. It is a disadvantage for the patient that several catheters are used in conjunction with the treatment. The patient may experience several changes of catheters as unpleasant and to some extent painful.
It is an objective of the invention to overcome the abovementioned problems. It is thereby possible according to the invention to obtain improved efficiency for treatment at the same time as the pain sensations of the patients are lessened.
According to one embodiment of the invention a combined anesthetic and treatment catheter is used. The treatment part thereof comprises a heating device inside a catheter sheath. Anesthesia of the prostate tissue is implemented by the use of at least one needle extending from the catheter sheath. The needle may be combined with temperature sensors.
According to a second embodiment there are no heating means present. Also in this embodiment there is a needle extendible from the catheter. The needle supplies medicine with a combined anesthetic and astringent effect.